Multiple Causal Links Between Magnocellular–Dorsal Pathway Deficit and Developmental Dyslexia

Abstract

Although impaired auditory-phonological processing is the most popular explanation of developmental dyslexia (DD), the literature shows that the combination of several causes rather than a single factor contributes to DD. Functioning of the visual magnocellular-dorsal (MD) pathway, which plays a key role in motion perception, is a much debated, but heavily suspected factor contributing to DD. Here, we employ a comprehensive approach that incorporates all the accepted methods required to test the relationship between the MD pathway dysfunction and DD. The results of 4 experiments show that (1) Motion perception is impaired in children with dyslexia in comparison both with age-match and with reading-level controls; (2) pre-reading visual motion perception-independently from auditory-phonological skill-predicts future reading development, and (3) targeted MD trainings-not involving any auditory-phonological stimulation-leads to improved reading skill in children and adults with DD. Our findings demonstrate, for the first time, a causal relationship between MD deficits and DD, virtually closing a 30-year long debate. Since MD dysfunction can be diagnosed much earlier than reading and language disorders, our findings pave the way for low resource-intensive, early prevention programs that could drastically reduce the incidence of DD.

Action Video Games Improve Direction Discrimination of Parafoveal Translational Global Motion but Not Reaction Times

“…In fact, it has been shown that playing AVGs enhances a range of cognitive abilities including working memory (Gong et al, 2016), spatial cognition (Feng et al, 2007), response selection and execution (Hutchinson, Barrett, Nitka, & Raynes, 2016), object tracking (Green & Bavelier, 2012), visual selective attention (Chisholm & Kingstone, 2015;Green & Bavelier, 2003) and motion perception (Green, Pouget, & Bavelier, 2010b;Hutchinson & Stocks, 2013). In addition, training on AVGs improves reading abilities in children with developmental dyslexia (Franceschini et al, 2013;Franceschini et al, 2015;Gori, Seitz, Ronconi, Franceschini, & Facoetti, 2015) (see Karimpur & Hamburger (2015) for a review on the role of AVGs in psychological research). Hutchinson and Stocks (2013) found that action video game players have lower coherence threshold for radially moving patterns (e.g., contracting vs. expanding motion), but not for translational or rotational moving patterns presented in the fovea.…”

Visual motion and rapid auditory processing are solid endophenotypes of developmental dyslexia

“…Similarly, pre‐readers at risk for DD have problems with motion perception tasks (Kevan & Pammer ; Boets et al . ; Gori et al ., ,b). Visual motion perception is the process of inferring the speed and direction of elements in a scene based on visual inputs (Albright & Stoner, ).…”

Two Visual Training Paradigms Associated with Enhanced Critical Flicker Fusion Threshold

“…This model links mechanisms of visual motion processing, and temporal processing, such as CFFT with the effective development of reading (Gori et al, 2014; Holloway, 2016). Supporting this model, Gori et al (2015) conducted multiple studies examining the relationship between dot-motion processing and reading, including showing that dot-motion training led to improvements in reading in participants with dyslexia. Similarly, Polat et al (2012) and Deveau and Seitz’s (2014) presented evidence that contrast sensitivity training also improved normal people’s reading speed.…”

“…Here, we examine this idea by examining two different visual training approaches; random dot-motion (Gori et al, 2015) and contrast sensitivity training (Deveau et al, 2014) that have been shown to transfer to reading performance. We examine how they impact critical flicker fusion thresholds (CFFTs); a basic visual processing skill (the ability to process a rapidly flickering light until it perceptually fuses into a steady light or perceptually translates from a steady to a flickering light) that has been linked with reading proficiency (Holloway et al, 2013).…”

“…CFFT was previously thought to be a stable individual-specific function over time, shown to correlate with some cognitive processes related to intelligence (Tanner, 1950; Zlody, 1965) and word decoding ability in reading both real words and meaningless pseudo-words (Holloway et al, 2013). However, CFFT has been shown to be mutable through training on dot-motion tasks (Seitz et al, 2006) and has been hypothesized to be a route to improving reading skills (Holloway et al, 2013; Gori et al, 2015). While correlational, a result showing that both contrast sensitivity training and dot-motion training result in CFFT enhancement would support a model that CFFT improvement is related to the observed reading benefits found through these trainings.…”